During a vehicle brake application fluid pressure is communicated to a front wheel brake assembly and a rear wheel brake assembly. As the vehicle decelerates the weight of the vehicle is shifted from the rear wheels to the front wheels so that the traction between the surface and front wheels is greater than the traction between the surface and the rear wheels. If equal fluid pressure is continuously communicated to front and rear brake assemblies, the rear wheel assembly will tend to lock up, thereby creating a dangerous skidding condition for the rear wheels.
In order to avert the above skidding condition for the rear wheel assembly it is common practice to provide a proportioning valve which is disposed within the brake fluid line. The proportioning valve is either pressure or load sensitive to restrict communication of fluid pressure to the rear brake assembly during a brake application.
Heretofore, the proportioning valve has been integrated into a master cylinder or provided as a separate assembly within the brake fluid line between the master cylinder and a wheel cylinder of the rear brake assembly. As a separate assembly the proportioning valve has required a housing and fittings for coupling the separate assembly within the brake fluid lines and as a part of the master cylinder the proportioning valve has required modifications to the master cylinder to dispose the proportioning valve within or in attachment to the master cylinder.